The present invention relates to a method for assembling a car body, and more precisely to a method for framing of car body components. The invention relates further to an arrangement and an apparatus for use in car body assembly.
In the manufacture of cars, especially when manufacturing the bodies of the cars the conventional systems comprise a body assembly line, on which the bodies are assembled and forwarded as the assembly work proceeds. A framing station is positioned on said assembly line, said framing station forming one of the key elements of the assembly line. Said framing station is used for accurately positioning body components, such as a bottom plate, side panels, rear and front cross members of the body, engine compartment, roof etc., relative to each other. The body components may have been loosely preassembled in the previous stages in the assembly line. Said framing station is used also for welding of the accurately positioned body components together to form a solid car body.
A conventional framing station system usually comprises a heavy and fixedly mounted frame (or gage) structure enclosing the framing station and suitable rigid holding means for holding the loosely preassembled body components together during the welding operations.
FIG. 1 is a schematic presentation of one prior art framing arrangement in which heavy jigs are utilized, It is noted that the heavy frame structure has been omitted from FIG. 1 to clarify the general presentation. The prior art jigs such as disclosed by FIG. 1 do usually have a weight which exceeds 1000 Kg per a jig. This leads to a heavy and costly apparatus for the handling thereof during the car body assembly operations.
U.S. Pat. No. 4,667,866 (Tobita et al.) discloses a framing station mounted fixedly on an assembly line. This prior art framing station has a corresponding heavy frame structure as was described above and utilizes several jigs which are moved into and within and out from the framing station or main assembly station. More precisely, the jigs are moved by an independent conveyor each to the main framing station and subsequently by a special, fixedly mounted positioning devices of a xe2x80x9cbody assemblerxe2x80x9d within the framing station. The system comprised a heavy frame construction, and a plurality of different kinds of conveyors and fixedly mounted handling apparatus for the substantially large and heavy jigs. Therefore the flexibility of the system is not considered to be adequate to fulfil the requirements set for a flexible manufacture of car bodies.
According to one another approach, disclosed eg. by U.S. Pat. No. 5,011,068 (Stoutenburg et al.) and U.S. Pat. No. 5,427,300 (Quagline), essentially rigid and heavy pivotable arms or clamps are mounted on the top portion of the frame, usually such that they can be pivoted upwards and downwards about an essentially horizontal axis. When said arms are pivoted down to engage the loosely assembled body, they will rigidly clamp the body components (or members) together for the subsequent welding operations.
The above described known systems have various disadvantages. In most cases the jigs or the clamping arms are adapted to fit one body model only, and thus they have to be changed if other models are produced on the same manufacturing line. The remarkable weight of the jigs makes the moving and/or change of them complex and difficult and expensive to arrange. This all means limited possibilities for producing different car models in a same framing station. Eg. in so called revolver stations using clamping arms the number of different models is usually restricted to four. This in turn is against the modern ideas of so called flexible manufacturing, according to which the manufacturing systems should allow as high flexibility in view of various car models as possible. In addition, even though some prior art framing stations allow framing of several models in one framing station, the number of different models is generally still restricted to those models which can be formed on the same bottom plate of one single car body type.
In addition, the conventional framing stations as discussed above are expensive and the built-up time thereof (ie. the built-up of the complex and heavy frame construction and the different special conveyors) is remarkable long. As the expected life time of one single car model has shortened, and the amount of different car models has increased, the total number of individual body models to be produced has dropped dramatically. Therefore the built-up time and the costs of the conventional framing stations adapted only for one or for few car models only are far too high.
Furthermore, due to the heavy and space requiring jigs or clamping arms substantially covering the entire car body, the accessibility of the body itself, for example for the welding operations, is poor.
The rigid and for a certain car model or models customized prior art framing stations are built from special and unique components. In case of a machine breakdown, the repair usually needs special skills and/or unique replacement parts. This is a serious disadvantage, since even a minor failure in the framing station may lead into a situation, in which one of the key components of the car manufacturing might be out of operation for an essentially long time period. This can have serious effects for the entire manufacture of this certain car model, or several models. Even the car manufacturer as whole may suffer badly from this, as this one single failure may have disadvantageous effects eg. to the logistics management and reputation of the company.
There has been various prior art attempts to overcome the above and other disadvantages of the conventional systems. From these WO publication 95/132886 discloses an arrangement which utilizes five or six holding frames, wherein the body will become cubically surrounded and supported from all sides thereof by means of said holding frames. At least some of the body components are attached to the holding frames prior to the assembly, and they are brought to the framing station and engaged with the body by means of one of said holding frames, which in turn is moved by a manipulator. The holding frames are rigidly attached to each other by positioning devices in the corners thereof such that they are positioned in an exact 90xc2x0 angle relative to each other. As mentioned, this holding frame assembly surrounds the car body cubically from four sides and from the top.
However, it is considered that such arrangement would form a too heavy construction to be handled by conventional manipulators and especially by industrial robots, which in most cases are only capable of handling of loads less than 300 kg, and usually less than 200 kg. If the costs of the required apparatus are taken under consideration, the increased requirements for the load capacity requirements will rapidly increase costs of the required manipulators or industrial robots too high to be realistic. Thus, when several of them are required per one framing station, this will cause such an increase in costs that the arrangement according to WO 95/32886 is no longer considered as economically profitable, if possible at all.
In addition to the heavy structure, the holding frame of WO 95/32886 surrounds the car body in a manner which hinders the accessibility to the body and thus makes the welding operations more difficult to perform. The general construction of this supporting frame is also such that the beams of the holding frames are spaced well apart from the body, and thus different longitudinal supporting elements has to be used between the beams and the body. This increases further the weight, size and the complicity of this known structure. As the size and weight of one single holding frame component is essentially big due to the general shape and heavy construction thereof, the number of different holding frame components needed for several body models require a remarkable area for storage. Furthermore, the body components has to be preassembled into the holding frame components in a separate station, which means one additional step for the framing process. The disclosed locking arrangement requires also exact 90xc2x0 joints between the frame components and a complex positioning device in each of the corners thereof.
Thus there is still a need for an improved framing method and arrangement and apparatus which could allow a flexible manufacture of car bodies without the above mentioned drawbacks of the prior art systems.
Accordingly, it is an object of the present invention to overcome the disadvantages of the prior art arrangements and to provide an improved solution for enabling a flexible car body framing.
It is an object of the present invention to provide a method and arrangement by means of which it is possible to move the required supporting means by a standard industrial robot.
It is an object of the present invention to provide a method, an arrangement and an apparatus which enables a use of a net-like supporting structure which is assembled from several separate supporting elements, said net-like structure allowing a good accessibility to the body.
It is an object of the present invention to provide a method, an arrangement and an apparatus which minimizes the set-up times of a framing station between different car body models.
It is an object of the present invention to provide a method and an arrangement by means of which it is possible to avoid essentially long reparation times in case of a machine failure in the arrangement according to the present invention.
It is an object of the present invention to provide a method, an arrangement and an apparatus which provides an improved solution for locking several support elements to each other and to form a clamping net structure for supporting the car body.
It is an object of the present invention to provide a method and an arrangement which saves the floor space and by means of which is possible to shorten the entire length of a car body assembly line.
Other objects and advantages of the present invention will be brought out in the following part of the specification taken in conjunction with the accompanying drawings.
The invention is mainly based on the idea that by providing a new type light-weighted supporting means network consisting of a number of separate custom shaped and dimensioned support elements rigidly locked to each other in an inventive manner around a preassembled car body, wherein robots or similar means are utilized both in body component and support elements handling, an improved flexible and automatic solution for car body framing is provided.
More precisely, the present invention is characterized by what is disclosed in the appended claims.
According to a preferred embodiment of the present invention, a method for framing a car body from a plurality of separate body components comprises steps for attaching a bottom plate of the car body to a bottom plate support means, bringing at least a part of the separate body components into engagement with the bottom plate by means of a robot or similar apparatus, preassembling the body components relative to the bottom plate and/or relative to each other so that a preassembled car body having the external shape of the car body becomes achieved, and forming a support means from a plurality of separate support elements for supporting the preassembled car body such that at least a part of the support elements is brought into engagement with the bottom plate support means and/or another support element by means of a robot or similar apparatus. The support elements are clamped to each other in order to form a support means net, wherein the forming of the support means net is accomplished such that each of the support elements is clamped either to at least two other support elements and to the bottom plate support means or to at least three other support elements by means of locking unit means provided in the support elements.
In addition, the invention provides a framing station arrangement for car body framing from a plurality of separate body components, comprising a bottom plate support means for receiving and supporting a bottom plate of a car body, attachment means for clamping the bottom plate on the bottom plate support means, a robot or similar apparatus for bringing at least one of the separate body components into engagement with the bottom plate, means for preassembling said body components relative to the bottom plate and/or relative to each other so that the external shape of the car body is achieved, a support means formed by a plurality of separate support elements for supporting the preassembled car body, and a robot or similar apparatus arranged to bring at least one of the support elements of said plurality of support elements into engagement with said bottom plate support means and/or at least one another support element. In accordance with the invention the support means are arranged to form a support means net such that each of the support elements forming said support means net is clamped either to at least two other support elements and to said bottom plate support means or to at least three other support elements by means of locking unit means provided in the support elements.
A support apparatus for car body framing from a plurality of separate body components is comprising in combination the following elements: a bottom plate support means for receiving and supporting a bottom plate of a car body, attachment means for clamping the bottom plate on the bottom plate support means, attaching means for preassembling the separate body components relative to the bottom plate and/or relative to each other so that the external shape of the car body is achieved, support means formed by a plurality of separate support elements arranged to be movable by a robot or similar apparatus and clamped to each other to form a support means net for supporting the preassembled car body such that each of the support elements forming the support means net is clamped either to at least two other support elements and to the bottom plate support means or to at least three other support elements by means of locking unit means provided in the support elements, and gripping means for removably holding at least a part of the body components by the support means net.
Said support means net is preferably arranged such that the construction and shape thereof follows essentially the shape and construction of the car body while allowing an essentially good accessibility to the car body for the subsequent assembly operations.
It is noted that the in this context used definitions xe2x80x9cpreassemblingxe2x80x9d, xe2x80x9cpreassemblyxe2x80x9d or the equivalences thereof are intented to cover all such preparative operations, by means of which the car body will become lightly pre-assembled ie. the adjacent body members will become held relative to each other by more or less temporary binding means, such as clinching, welding, gluing, riveting or any other appropriate means.
Several advantages are obtained by means of the present invention, as the solution provides a reliable, automatic and flexible manner for car body framing.
In principle, the flexible solution according to the invention allows to produce car bodies in an arbitrary order such that the series size may be set to be as low as 1. There are no restrictions in view of the bottom plate either, and thus even different bottom plates may be used in subsequent operation cycles. In addition, as the arrangement utilizes standard components, such as standard industrial robots of substantially low costs, the maintenance and repair thereof as well as all changes for instance in the number and layout of the robots are easy and fast to perform. Thus invention provides a high level of automation by reasonable costs.
The size and weight of single framing elements forming the framing structure is reduced so much that even the ordinary industrial robots are capable of handling them. The assembly of a framing net structure from the separate framing elements is easy and fast to perform. Despite this the inventive framing structure will provide a rigid support for the body components or members while allowing a good accessibility, for instance for the welding robots. As the size of the framing elements is reduced, and the structure thereof is simplified, the storage space requirements thereof are also reduced. In addition, single framing elements are essentially cheap to manufacture and easy to handle and store, which enables a wide variety of custom fitted framing elements for a wide range of different car model in a manner which is economically more reasonable than in the known arrangements.